Pressure-balanced gear pump



Sept. 5, 1961 .1. c. LEE

PRESSURE-BALANCED GEAR PUMP 2 Sheets-Sheet 1 Filed April 25, 1958 Sept.5, 1961 J. c. LEE 2,998,783

PRESSURE-BALANCED GEAR PUMP Filed April 25. 1958 2 Sheets-Sheet 2,fm/enfor- J0/7/7 C. Le@

Patented Sept. 5, 1961 2,998,783 PRESSURE-BALANCED GEAR PUMP John C.Lee, 703 N. Elmhurst Ave., Mount Prospect, lll. Filed Apr. 25, 1958,Ser. No. 730,843 6 Claims. (Cl. 103-126) The present invention relatesto gear pumps, and more particularly to means for pressure-balancingintemal-gear pumps.

A principal object of the invention is to provide a construction andarrangement in an internal-gear pump in which uid pressure is utilizedfor counteracting the forces otherwise tending to cause deflection ofmoving parts and consequent wear to those'paits and other parts betweenwhich there is relative movement.

Another object is to provide in a gear pump of the character noted,greater sealing effect between relatively moving parts.

A further object is to provide a gear pump in which, because of thenovel arrangement of fluid-pressure balancing of the character referredto, the loads imposed on the moving parts are reduced, higher operatingpressures can be accommodated, and a more compact structure results withconsequent reduction in weight and cost.

Another object is to utilize the pressure-balancing system referred tofor positively lubricating certain internal relatively moving parts ofthe pump.

A still further object is to utilize the pressure-balancing arrangementreferred to, to provide more effective lubrication to the bearing forthe drive shaft of the pump and to prevent leakage through the seal forthe drive shaft.

Other objects and advantages of the invention will appear from thefollowing detailed description taken in conjunction with theaccompanying drawings in which- FIG. l is a longitudinal axial sectionalview, taken on a staggered line, vof a pump embodying the features ofthe present invention; and

FIG. 2 is a view taken substantially on line 2-2 of PIG. 1.

Referring now in detail to the drawings attention is directed first .toFIG. l showing the main parts of the pump of the present invention. Thepump illustrated is of the overhanging or cantilever type, as applied towhich the present invention is found to be unusually effective. The pumpincludes a housing 10 made up of a casing 12 and a head 14. Within thehousing 10 are a pair of gears which include a ring gear or rotor 16 anda pinion gear or idler 18. The ring gear or rotor 16 is connected to adrive shaft 20 for rotation by an external source, such as a motor (notshown), and the idler gear 18 is mounted on a fixed pin 22 mounted inthe head 14. Upon rotation of the gears in a first direction, which inthe example assumed throughout this specification is counterclockwise asviewed in FIG. 2, the fluid to be pumped enters into the suction passage24 and emerges through the discharge passage 26 formed in the casing 12.Further details of these main parts will be described hereinbelow.

The housing 10 includes a gear chamber 28 which is defined by the casing12 and the head 14, in which the gears 16 and 18 are confined andpositioned for rotation.

The casing 12 includes a main body portion 30 having a shaft opening 32for receiving the drive shaft 20 and opening into the chamber 28. Thisopening includes a recess 34 next adjacent the ,chamber 28, forreceiving the hub 36 of the ring gear or rotor 16; next thereto is areduced diameter portion 38 for receiving a casing bearing 40 whichdirectly supports the drive shaft 20; the opening 32 also includes acounterbore portion 42 rearwardly of the portion 38 in which is disposeda shaft seal 44 of conventional construction, held in place by afollower 46 having a ange 48 through which bolts 50 are inserted intotapped holes in the body 30 of the casing. The casing body 30 has anextension 52 in which is disposed a conventional ball bearing 54 forsupporting the drive shaft 20 at this point, the shaft then beingsupported at two widely spaced points, namely, the bearings 40 and 54,for maintaining the drive shaft, and thus the ring gear or rotor 16,accurately in position.

Formed in the body 30 of the casing 12 are a pair of return ventpassages 56 and 58 communicating with the opening 32 at a pointapproximately between the bearing 40 and seal 44 at one end, and thechamber 28 of the casing at the other end. One of the passages, such asthe passage 56, communicates with the chamber 28 in the suction passage24, and the other return vent passage 58 communicates with the chamber28 in the discharge passage 26. A pl-ug 60 is removably positioned inone of the passages, such as by threading it in place, so that it can bepositioned selectively in either of the passages for blocking thatpassage, it being understood that the pump is reversible and the suctionand discharge passages are such depending upon the direction ofoperation of the gears. However, in the example assumed herein, thepassage 24 will be regarded as the suction passage and therefore thepassage 56 is connected to its side of the interior of the pump. If itshould be desired to reverse the direction of the pump, the insert plug60 is removed from the passage 58 and placed in the opposite passage 56.

The chamber 28 has axially opposite end faces 62 and 64, the rear one ofwhich, 62, is formed on the casing 12 while the front one, 64, is formedon the head 14. These end faces are accurately finished for producingeffective sealing spaces with the corresponding and adjacent surfaces ofthe gears 16 and 18. The rear end face 62 is annular inishape,surrounding the recess 34 and is provided with recessed portions 66providing free flow of fluid from the respective return vent passages 56or 58 into the respective suction or discharge passage 24 or 26. Theserecessed portions 66 may be of any desired circumferential extent. Thefluid pumped is free to flow past the periphery of the rotor 16 throughthe recessed portions 66, or through the space 68, into the space 70,namely, the space between the rotor 16 and the end face 62. The rearsurface of the disc 72 of the rotor 16 is accurately finished, and thespace 70 is of small dimension and acts as a sealing space against thefree flow of fluid therethrough. However, as in a pump of this generalnature, there is of course, a certain minor amount of flow of uidthrough all such spaces.

The hub 36, referred to above, s received in the recess 34, beingsecured to the drive shaft 20 by any suitable means such as a pin 74.The space 76 between the hub 36 and the recess 3'4 is preferably ofrelatively great dimensions, for relatively freer flow of uidtherethrough. Extending forwardly from the periphery of the disc 72 area plurality of teeth 78, which in the form of pump utilized, are eightin number, -as seen in FIG. 2. These teeth extend into effective sealingengagement with the front end face 64 on the head 14 for forming a space80 which is of dimensions similar to those of the space 70. The spaceserves as an effective seal against the free flow of fluid therethrough.Between the teeth 78 are cavities 82 for receiving fluid from thesuction passage 24 and carrying it through the pump, as describedhereinbelow.

Thesuction passage 24 includes a chamber-like portion 84 surrounding asubstantial portion of the periphery of the rotor 16 and a terminalportion 86 formed in a tubular element 88 of the casing serving as anadaptor for connection to a conduit. charge passage 26 includes achamber-like portion 90 and a terminal portion 92 formed in a tubularportion 94,

In a simil-ar manner the dis- 3 The casing is shaped for engagement bythe gears, on one side by a surface portion 96 (FIG. 2), and on theopposite side by a surface portion 98, both engaged by the teeth 78.Other elements cooperate to effectively separate the suction anddischarge passages, as described below.

The rotor or ring gear 16, as will be understood, meshes with the pinionor idler 18. The idler is mounted on the pin 22 in a conventionalmanner, having a bearing 100 interposed therebetween. The outer portion102 of the body of the idler is accurately finished on the axiallyopposite surfaces for effective sealing engagement with thecorresponding surfaces of the disc 72 and front end face 64, for formingspaces 104 therewith, serving as sealing spaces against the free flow offluid. The idler 18 has teeth 106 forming cavities 108 therebetween, theidler in the design utilized for illustration herein having six teethand cavities.

The rotor 16 and idler 18, as will be observed from FIG. 2. arerelatively eccentrically mounted and the meshing engagement between thegears takes place at one side of the pump, the right side-FIG 2. Thesectional view of FIG. l is taken on a staggered line, the right andleft portions, as measured by the length of the shaft and pin 22, beingtaken substantially on the axes of those V members, respectively.Adjacent the opposite side is a crescent 110 secured to or integral withthe head 14 and extending into effective sealing engagement with theopposed surface of the disc 72 for providing effective sealingengagement against the free flow of fluid therepast.

The gears 16 and 18 engage the crescent in their rotation in such a waythat closed cavities indicated at 108a, and 82a and 82h, are formed forcarrying fiuid from the suction passage to the discharge passage. In thedischarge passage side of the pump, the teeth intermesh and force theuid from the cavities.

Holes 112 are formed in the disc 72 for establishing communication onopposite sides of the disc 72, for accomplishing an advantage explainedmore fully hereinbelow. These holes preferably are located adjacent toand radially inwardly of the respective teeth 78.

Means is provided for balancing the pinion or idler 18 through theinstrumentality of supplying tiuid under pressure to axially oppositesides of the idler. Formed in the head 14 are a pair of return ventpassages 114 and 116 communicating respectively between the suctionpassage 24 and the discharge passage 26, and a groove 118 in the head 14surrounding the pin 22. The pin is provided with a bore 120communicating between the groove 118 and the space between the pin andthe bearing 100.

The bearing 100 and the adjacent portion 122 of the idler are of axialdimension less than the axial spacing between the end faces 62 and 64,leaving spaces 124 of substantially greater dimension than the sealingspaces 104. The

passage 114 is provided with a removable plug 126 closing that passagefrom the suction side, but the passage 116 from the discharge sideremains open. Such a removable plug is utilized for enabling its usealternatively in either of the passages laccording to the direction ofoperation of the pump, as explained above in connection with thepassages 56 and 58. In the operation of the pump, the greater pressureof the fluid in the discharge passage of the pump is forced through thepassage 116, the groove 118 and the bore 120 into the space between thepin and the bearing 100, from which it enters into tilting and cockingof the ring gear or rotor. In addition, the pressures in the cavities inthe gears vary from one side of the pump to the other and tend toproduce a further binding or cocking effect on the rotor 16. The presentinvention counteracts such an effect by establishing a fiuid pressure onthe rear side of the disc 72 similar to that on the front side, varyingin accordance therewith; the spaces 68 and 66 enable relatively freeflow of fluid from the suction and discharge passages into the space 70between the disc 72 and the rear end face 62, and therefore the fluidpressures throughout this space 70 assume a pattern closely similar tothe pattern of distribution of pressures on the front-side of the disc,i.e., adjacent the suction passage 24 where the fluid pressures in thepump are relatively low, there is a relatively low fluid pressure on therear side of the disc; similarly, at the discharge side of the pumpthere is a higher uid pressure on the front side of the disc, and sincethe uid can fiow relatively freely from the discharge passage into thespace behind the disc, the disc at the discharge side has relativelyhigh fluid pressure on both sides.

To aid in establishing these equal pressures on opposite sides of thedisc, and thus balancing the ring gear 16, the holes 112 in the disc 72are provided which establish direct communication between the cavitiesin the gears and the space 70 behind the disc. In addition to thegeneral and overall increase of fluid pressure from the suction side tothe discharge, there is an irregular pattern or distribution of fluidpressures through the gears, or in the different cavities. The holes 112provide direct communication between each of the cavities individuallyand the adjacent portion of the space on the rear side of the disc sothat at each portion of the disc at any location around the disc, thehuid pressures on opposite sides of the disc are substantially equal.

Due to these equal fluid pressures on opposite sides of the disc, thering gear or rotor 16 is maintained in a perfectly true and accurateposition, there being no binding or cocking effect thereon as wasproduced in pumps of the kinds heretofore known. In such known pumps thebinding or cocking action was so great as to cause bending of the driveshaft and hence undue wear of the bearings such as 40 and 54, as well asdefection of the seal 44. Moreover, and `what was more serious, thevarious parts of the pump were required to be much heavier and strongerto withstand the binding and cocking forces. As a consequence, the pumpwas required to be more massive and heavy, while as contrastedtherewith, the pump made according to the present invention may be madeof much smaller and lighter parts. An important aspect of the balancingeffect is that the discharge pressures of the pump are not limited byreason of limitations necessarily placed on the strength of the parts inthe pump as in the case of prior pumps.

Due to the return vent passage 56, an additional balancing effect isproduced on the ring gear or rotor 16. A reduced pressure is produced inthe space 76, which counteracts any counter-force tending to be producedby the closed cavities 108:1, and 82a and 82h (FIG. 2), in which thereis, of course, a reduced fluid pressure. The holes 112 associated withthese closed cavities are at the time closed by the crescent 110, theholes being located adjacent the radially inner surfaces of the teeth 78so as to prevent any blocking effect of the fluid in the cavities by themeshing of the teeth-see extreme right FIG. 2. l

The reduced uid pressure in the shaft opening 32 produced by the returnvent passage 56 produces a more effective lubricating action in thebearing 40. It will be recalled that there is a relatively high pressurein the space 70 at the discharge side of the pump and uid therefromflows from this location through the space 76 to the bearing 40.

The reduced pressure just referred to also has the advantage of reducingor eliminating possible. leakage through the seal 44 because of the factthat the such reduced pressure is less than atmospheric pressure.

The balancing action on the pinion or idler 18is essentially a separateaspect from the balancing action on the rotor 16. The fluid from thedischarge side of the pump, as explained above, is forced through thepassage 116, groove 118, bore 120 through the space between the pin 22and the bearing 100 into the spaces 124. Because of the relativelygreater pressure of the lluid in these spaces, tluid is maintainedtherein at all times and results in substantially equal pressures onboth sides. Any tendency of the pinion or idler to oat forwardly orrearwardly is resisted by the uid in the corresponding space 104 and asa result the idler is maintained out of actual contact with both thedisc 72 and the front end face 64. Consequently, wear between theseparts is reduced and substantially eliminated. There is no tendency forthe idler 18, as made according to the above considerations, to bind ortilt or cock either from any similar inaccurately directed forces fromthe rotor 16 or from other forces including any resulting from the flowof nid or its mounting on the gear 22.

Due to the greater sealing area in the space 70 as compared with priorknown pumps there is less leakage and consequent higher volumetriceiliciency. However, notwithstanding such greater sealing area, theviscous drag torque is reduced because the area is closer to the axis ofrotation, as compared with the sealing areas in prior pumps around theperiphery of the rotor.

While I have disclosed herein a preferred form of the invention, it willbe understood that variations may be made therein without departing fromthe spirit and scope of the appended claims.

I claim:

1. An internal-gear pump comprising a housing having a chamber 'withaxially opposite end faces, and an inlet passage leading to the chamberand an outlet passage leading therefrom, a rotor gear having a disc andaxially extending teeth at its periphery, said rotor gear havingpassageways through said disc adjacent the innermost extreme of saidteeth mounted for rotation in said chamber with its disc disposedadjacent one of said end faces, the space between said disc and theadjacent said face being of substantially uniformly sealing-eiectdimensions entirely therearound, a drive shaft connected with said rotorgear and extending to the exterior, an idler gear within the rotor gearand having its axially opposite sides adjacent said'disc and theopposite end face respectively, said gears having intermeshingengagement at one side throughout their axial extent and formingcavities therebetween into which iluid is drawn from the inlet passageand from which it is expelled into the outlet passage, the housinghaving elements in cooperation with the teeth of the gears closing thecavities to the inlet and outlet passages at` intermediate pointstherebetween with the rotor gear engaging the idler gear. so that saidpassageways through the disc are uncovered in all positions ofengagement to prevent any blocking etect of the iluid in the cavitiesformed by the meshing of the teeth whereby said passageways providecommunication between said inlet and outlet passages and the respectiveadjacent portions of said space, and between said cavity and the sealingspace between the outer end wall of the disc and said one end wall ofthe housing chamber at all times during the engagement of said teeth forestablishing substantially equal fluid pressures on opposite sides ofsaid disc at all points therearound.

2. The invention set forth in claim 1 which said equal pressures areestablished by said passageways through vsaid disc, one such passagewaybeing disposed adjacent to and radiallyinwardly of each of the teeth ofthe rotor gear and being disposed in theclosed cavity formed by the samesaid tooth of the rotor gear and the two adjacent teeth of the idlergear, the teeth on the two gears being so dimensioned that the rotorgear teeth do not completely till the space between adjacent idler gearteeth and the passageways remain constantly open at the side of thegears at which they mesh.

3. An internal-gear pump comprising a housing having a chamber withaxially opposite end faces, an inlet passage leading to the chamber,an'outlet passage leading from the chamber, a rotor gear having a discwith axially extending teeth at its periphery and mounted for rotationin said chamber with the disc in sealing rela-4 tionship adjacent one ofsaid end faces and the extended ends of said teeth in sealingrelationship adjacent the other of said end faces, a drive shaftconnected to said rotor gear and extending through a lluid seal to theexterior of said housing, a pinion gear within said housing having oneaxial side in sealing relationship against said disc and the other axialside in sealing relationship against said other end face, said piniongear having a smaller diameter than said rotor gear, being mounted on anaxle parallel to and eccentric to the axis of said rotor gear, havingits teeth intermeshing in fluid sealing engagement with the teeth ofsaid rotor gear on one side and having indentations between adjacentteeth that are sufliciently deep so that the teeth of said rotor gear donot extend to the bottom thereof, means associated with said housinglocated diametrically opposed to the engaged portions of said gears andshaped to maintain sealing contact with the tips of the pinion gearteeth on one side thereof vand with the tips of the rotor gear teeth onthe other side thereof to provide a Huid seal between the inlet passageand outlet passage, venty holes through said disc, said vent holeslocated immediately adjacent the tip of each of said rotor gear teeth soas to prevent any blocking effect of the fluid in the cavities formed bythe meshing of the teeth to provide open communication through said discinto the sealing space between the outer end wall of the disc and saidone end wall of the housing chamber at all times during the engagementof the rotor gear teeth with the pinion gear teeth.

4. The intemal-gear pump of claim 3 further characterized in thatchannel means in said housing and in the axle of said pinion gear forman open communication between the outlet passageway and a point midwayaxially of said pinion gear andbetween said pinion gear and its axle.

5. The gear pump of claim 4 further characterized in that axiallyopposite sides of said pinion gear have shallow annular cavitiesadjacent the axle of said pinion gear.

6. The internal gear pump of claim 3 further characterized in thatchannel means in said housing forms an open communication between theinlet passageway and the iluid seal of the drive shaft.

References Cited in the le of this patent UNITED STATES PATENTS1,379,248 Carrey May 24, 1921 1,636,259 Sweeney July 19, 1927 1,816,508Wilsey July 28, 1931 1,928,300 Peltier Sept. 26, 1933 2,062,045 VanDeventer Nov. 24, 1936 2,124,140 Foster et al. July, 19 1938 2,516,589Pond et al. July 25, 1950 2,626,570 Armington et al. Jan. 27, 19532,650,544 Parsons Sept. 1, 1953

